Curable silicone rubber compositions to be cured by a curing addition reaction are well known. These curable silicone rubber compositions have good weather resistance, heat resistance, and electrical insulation and, therefore, used as a molding material for electric and electronic parts such as a gasket material, potting material, a coating material, a roll material and a casting material; a wire-covering material and an automobile part. Additionally, they are used as an encapsulating material and an adhesive material for an optical semiconductor on account of their optical property.
The curable silicone rubber compositions have siloxane bonds which are inherent in a silicone and, therefore, cannot sometimes exert the excellent properties of silicones such as chemical resistance, water-proof property and gas permeability due to the ion binding property of the siloxane bonds in extremely severe environments such as hot and humid environments. The surface of the cured products obtained from the curable silicone rubber compositions has tacking which cause problems such as sticking of dust. Further, the polymer having siloxane bonds has good gas permeability and used as an oxygen enrichment membrane. However, when this is used as an encapsulating material for an optical semiconductor, the moisture permeability is detrimental.
Various kinds of polymers and encapsulating materials which contain an isocyanuric ring are known. Japanese Patent Application Laid-Open No. 2008-143954 (Patent Literature 1) describes a cured product prepared by an epoxide ring-opening reaction of an isocyanuric ring-containing polysiloxane which is prepared by an addition reaction of an SiH-containing polysiloxane with diallyl monoglycidyl isocyanurate. Japanese Patent Application Laid-Open No. 2008-150506 (Patent Literature 2) describes a cured product which is prepared by an addition reaction of an isocyanuric ring-containing polysiloxane with an SiH-containing polysiloxane. Japanese Patent Application Laid-Open No. Hei 9-291214 (Patent Literature 3) describes a cured product which is prepared by an addition reaction of a triallylisocyanurate with an SiH-containing polysiloxane. Japanese Patent No. 4073223 (Patent Literature 4), Japanese Patent Application Laid-Open No. 2006-291044 (Patent Literature 5) and Japanese Patent Application Laid-Open No. 2007-9041 (Patent Literature 6) describe a cured product which are prepared by an addition reaction of a polysiloxane which has an isocyanuric ring and an SiH group with an alkenyl group-containing compound.
However, the isocyanuric ring-containing polymer described in Patent Literatures 1 and 2 has siloxane bonds in the main chain and, therefore, flexible, but less compatible with a cross-linking agent. Further, the position of the alkenyl group in the isocyanuric ring-containing polymer is various, and thereby difficult to cure by an addition reaction. Therefore, a characteristic of a hydrosilylation (addition reaction), such as rapid curing reaction, is not exerted. The isocyanuric ring-containing polymers described in Patent Literatures 3 to 6 have high crosslink density, are rigid and have poor flexibility.
There has not been known any cured product which is prepared by an addition reaction of an isocyanuric ring-containing polysiloxane with an SiH group-containing polysiloxane, and which has good flexibility, curing property, compatibility, and optical property and low moisture permeability.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2008-143954
Patent Literature 2: Japanese Patent Application Laid-Open No. 2008-150506
Patent Literature 3: Japanese Patent Application Laid-Open No. Hei-9-291214
Patent Literature 4: Japanese Patent No. 4073223
Patent Literature 5: Japanese Patent Application Laid-Open No. 2006-291044
Patent Literature 6: Japanese Patent Application Laid-Open No. 2007-9041